Fluorocarbon purification process

ABSTRACT

A halocarbon product made from the reaction of excess hydrogen fluoride with a halocarbon, containing excess hydrogen fluoride as an azeotrope is purified by fluorination in the presence of additional halocarbon or halo-olefin.

This is a continuation division of application Ser. No. 08/190,709 filedFeb. 2. 1994, now U.S. Pat. No. 5,461,177 allowed, which is acontinuation of application Ser. No. 07/592,173 filed Oct. 9. 1990, nowabandoned, which in turn is a continuation of application Ser. No.07/417,650 filed on Oct. 4, 1989, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a process for the purification offluorocarbons and the recovery of hydrogen fluoride used in theirmanufacture.

In many processes for making fluorocarbons in order to obtain anadequate degree of conversion of the starting halocarbon, it isnecessary to employ an excess of hydrogen fluoride. It is highlydesirable for economic reasons to recover this excess hydrogen fluoride,e.g., so it can be recycled.

Many processes have been developed for this purpose. However, since someof the hydrogen fluoride may be combined with the product as anazeotrope or be present in a slight excess to the product, in many casesit is difficult to remove. Neutralization of such hydrogen fluorideleads to waste disposal problems and environmental concerns. Morecomplicated methods of separation lead to additional capital investmentbecause hydrogen fluoride is a hazardous and difficult to handlematerial.

Furthermore, the recovery of the hydrogen fluoride is complicated by theunsaturated compounds which may also be present as impurities. Thesematerials are particularly undesirable as contaminants as they may betoxic and for most uses their concentrations in the saturated productsmust be lowered to as low a level as is practically possible.Distillation and other conventional physical methods which may be usedto lower the concentrations of unsaturated products are generallyineffective if the boiling points are too close, and are generally toocostly. Therefore, various chemical treatments have been proposed.

None of these prior processes is entirely satisfactory from a commercialviewpoint. The aqueous alkaline metal permanganate treatments of the artrequire that the halocarbon products exiting the treatment medium bedried (separated from its entrained water) before further refining,which adds to the expense of the treatment. Moreover, where saturatedhalohydrocarbon products are being treated, the possibility exists thatsome of the valuable saturated material could be lost to the alkalineoxidative medium along with the unsaturated impurities.

Thus, an effective process must not only recover the combined hydrogenfluoride but must also take care of any unsaturated impurities present.

The process of the invention efficiently utilizes the combined hydrogenfluoride by reacting it with additional starting material or any othersuitable halocarbon or halo-olefin and also with the olefin which is inthe reaction product that is to be treated.

SUMMARY OF THE INVENTION

This invention provides for a process for the reduction of the hydrogenfluoride content of a halocarbon product made from the reaction ofhydrogen fluoride with a halocarbon by reacting the excess hydrogenfluoride, which is substantially combined as an azeotrope, withadditional halocarbon or halo-olefin, over a fluorination catalyst underfluorination conditions. The halocarbon product containing the hydrogenfluoride may also contain olefinic impurities which are converted tosaturated compounds during the fluorination.

DETAIL OF THE INVENTION

The invention may be applied to the reduction of the hydrogen fluoridecontent of saturated halocarbon products and mixtures thereof, preparedby reaction with hydrogen fluoride and which contain one or morefluorine atoms in the molecule, and if they contain more than one carbonatom may be contaminated with olefinic impurities. Included arechlorofluoro- and fluorohydrocarbons composed of: carbon, hydrogen,chlorine and fluorine, and carbon, hydrogen and fluorine. The saturatedhalocarbons and/or mixtures thereof preferably contain 1 to 6 carbonatoms, more preferably 1 to 3, most preferably 1 to 2 because of theirgreater commercial importance.

The saturated halocarbons and/or mixtures thereof include cyclic as wellas acyclic compounds represented by the empirical formulaC_(a)H_(b)Cl_(c)F_(d) where a is an integer from 1 to 6, b, c and d areintegers from 1 to 13, provided that b+c+d equals 2a+2 when the compoundis acyclic and equals 2a when the compound is cyclic.

In a preferred embodiment the halocarbons are acyclicchlorofluorohydrocarbons, represented by the above empirical formulawhere a is 1 to 3, b and c are 1 to 7 and is 1 to 7.

In another preferred embodiment the halocarbons are acyclicfluorohydrocarbons represented by the above empirical formula where a is1 to 3, b is 1 to 7, c is 0, and d is 1 to 7, and b+d equals 4 when aequals 1, equals 6 when a equals 2, and equals 8 when a equals 3.

Representative saturated halocarbons that can be treated in accordancewith the method of the invention include chlorofluorohydrocarbons suchas CHClF₂, CF₃CHCl₂ and CF₃CHClF; and fluorohydrocarbons such asCHF₂CHF₂ and CF₃CH₂F.

The above saturated halocarbons are produced by processes that result inthe product containing excess hydrogen fluoride, usually combined as anazeotrope. The composition of this azeotrope will vary depending on theproduct halocarbon. In some embodiments, if the excess hydrogen fluorideis not all combined to form an azeotrope, the product mixture can firstbe subjected to a conventional separation process to remove theuncombined hydrogen fluoride and other easily separated material. Inother embodiments, the product mixture will contain unsaturatedimpurities. By easily separated materials is meant materials havingboiling points sufficiently far apart to make an economic separationfeasible, e.g., distillation.

As set forth above, the product mixture contains the excess hydrogenfluoride as an azeotrope. This is an azeotrope of hydrogen fluoride withthe halocarbon of the formula C_(a)H_(b)Cl_(c)F_(d) where a, b, c and dare as previously defined.

The product mixture after separation of its easily separated components,is then fed into a reactor where it is contacted with additionalhalocarbon under fluorinating conditions in the presence of afluorination catalyst.

The additional halocarbon which is reacted with the excess hydrogenfluoride azeotrope can be represented by the empirical formulaC_(a)H_(b)Cl_(c)F_(d) where a is an integer from 1 to 6, b and a areintegers from 0 to 13, and a is an integer from 1 to 13, provided thatb+c+d equals 2a+2 when the compound is acyclic and equals 2a when thecompound is cyclic.

The additional halo-olefin which is reacted with the excess hydrogenfluoride azeotrope can be represented by the empirical formulaC_(a)H_(b)Cl_(c)F_(d) where a is an integer from 2 to 6, b and d areintegers from 0 to 11, and c is an integer from 1 to 11, provided thatb+c+d equals 2a when the compound is acyclic and equals 2a−2 when thecompound is cyclic.

Conventional fluorination catalysts and conditions can be used in theprocess of the invention.

The catalytic systems needed to effect the reaction of the producthalocarbon/hydrogen fluoride mixture with an additional halocarbon canemploy both vapor and liquid phase approaches. Examples of vapor phasecatalysts and procedures for their use in fluorination reactions aredescribed in U.S. Pat. Nos. 4,766,260, 3,258,500, and in the referencescited therein. Examples of liquid phase catalysts and procedures fortheir use in fluorination reactions are described in U.S. Pat. Nos.4,374,289, 4,258,225, and in the references cited therein.

The reaction vessel is constructed from materials which are resistant tothe action of hydrogen halide such as Hastelloy® nickel alloy orInconel® nickel alloy.

The purified halocarbons are useful as refrigerants, blowing agents andsolvents.

A process is provided in accordance with this invention for thereduction of the hydrogen fluoride content of fluorocarbons by reactingexcess hydrogen fluoride with a halocarbon comprising: (a) feeding ahalocarbon product mixture containing an azeotrope of hydrogen fluoridewith at least one compound of the formula C_(a)H_(b)Cl_(c)F_(d), where ais 1 to 6, b is 1 to 13, c is 1 to 13 and d is 1 to 13, provided thatb+c+d equals 2a+2 when the compound is acyclic and 2a when it is cyclic,into a reactor; (b) contacting the azeotrope of (a) with: (i) an amountof a compound of the formula C_(a)H_(b)Cl_(c)F_(d) where a is 1 to 6, bis 0 to 13, c is 1 to 13, and d is 0 to 13, provided that b+c+d equals2a+2 when the compound is acyclic and 2. when it is cyclic; or, (ii) anamount of a halo-olefin of the formula C_(a)H_(b)Cl_(c)F_(d) where a is2 to 6, b is 0 to 11, c is 1 to 11, and d is 0 to 11, provided b+c+dequals 2a when the compound is acyclic and 2a−2 when it is cyclic; theamount being in excess of the amount of hydrogen fluoride in theazeotrope with a fluorination catalyst under fluorinating conditions. Ahalocarbon product made from the reaction of excess hydrogen fluoride asan azeotrope can thus be purified by fluorination in the presence ofadditional halocarbons or halo-olefin.

As an example of the process, chlorodifluoromethane can be produced bythe reaction of CHCl₃ and hydrogen fluoride over a fluorination catalystsuch as SbCl₅, for example as described in M. Hudlicky, “Chemistry ofOrganic Fluorine Compounds,” 2nd (Revised) Ed., John Wiley, N.Y., 1976,p. 727. The reaction product stream contains hydrogen fluoride, CHClF₂,HCl, CHCl₂F, and minor amounts of other products. After separation ofHCl and most of the excess hydrogen fluoride, the stream containingCHClF₂ and the combined hydrogen fluoride is reacted with an additionalhalocarbon in a molar amount greater than the hydrogen fluoridecontained in the CHClF₂/hydrogen fluoride product stream to afford morehighly fluorinated halocarbons. Preferably the additional halocarbon isCHCl₃ and the more highly fluorinated halocarbons produced are CHCl₂Fand CHClF₂.

2,2-Dichloro-1,1,1-trifluoroethane (CF₃CHCl₂) and1,1,1,2-tetrafluoro-2-chloroethane (CF₃CHClF) can be produced by thereaction of hydrogen fluoride and tetrachloroethene (CCl₂═CCl₂) in thepresence of a selected metal on a high fluorine content alumina support;for example as described in U.S. Pat. No. 4,766,260. The reactionproduct stream contains hydrogen fluoride, HCl, CCl₂CCl₂, CF₃CHCl₂,CF₃CHClF and CF₃CHF₂. After separation of HCl, CCl₂═CCl₂, CF₃CHF₂ andmost of the excess hydrogen fluoride, the stream containing CF₃CHCl₂,CF₃CHClF and the combined hydrogen fluoride or optionally separateproducts containing CF₃CHCl₂ and combined hydrogen fluoride and CF₃CHClFand combined hydrogen fluoride is reacted with additional halocarbon ina molar amount greater than the hydrogen fluoride contained in theCF₃CHCl₂/CF₃CHClF/hydrogen fluoride or CF₃CHCl₂/hydrogen fluoride andCF₃CHClF/hydrogen fluoride product streams to afford more highlyfluorinated halocarbons. Preferably the additional halocarbon isCCl₂═CCl₂ and the more highly fluorinated halocarbons produced areCF₃CHClF, CF₃CHCl₂, CF₂ClCHCl₂ and CFCl₂CHCl₂.

In a similar manner, as described above for CHClF₂/hydrogen fluoride andCF₃CHCl₂/CF₃CHClF/hydrogen fluoride, CF₃CHCl₂/hydrogen fluoride andCF₃CHClF/hydrogen fluoride products, other halocarbon/hydrogen fluoridemixtures may be treated to reduce the hydrogen fluoride concentration ofthe product stream.

The process will be further illustrated by the following Examples.

EXAMPLES General Experimental Procedure for Liquid-Phase Reactions

The reactor consisted of a 100 mL high pressure cylinder made of Monel®nickel alloy or Inconel® nickel alloy containing a magnetic stirrer andan internal thermocouple. A condenser and a back-pressure regulator,connected to an optional on-line analytical system, were mounted on topof the reactor. Suitable inlet and exit lines were present to allow foradmission of reactants and withdrawal of products.

To the reactor was charged TaF₅ in the desired amount. The reactor wasthen cooled to −78° C. and the ambient atmosphere removed under vacuum.The reactants were added to the reactor, which was then pressurized withnitrogen to the desired pressure while still cold. The reactants weregradually heated to the desired operating temperature with stirring,with external heat provided by an oil bath. The back-pressure regulatorwas set to the desired operating pressure prior to heating the reactor.

At the completion of the reaction, the reactor contents were cooled toroom temperature and the product composition determined by gaschromatography. The percentages reported in the Examples are in area %unless otherwise indicated.

Example 1 Reaction of Hydrogen Fluoride/1,1,1,2-Tetrafluoroethane withTrichloroethene

The General Experimental Procedure for liquid-phase reactions wasfollowed using TaF₅ (3.0 g, 0.011 mol), CF₃CH₂F (25 mL, 0.30 mol),anhydrous hydrogen fluoride (1.25 mL, 0.063 mol), the HF and CF₃CH₂Famounts were selected so as to simulate an azeotropic composition, andCHCl═CCl₂ (10.0 g, 0.076 mol). The reactor was pressurized to 200 psigwhen cold (−78° C.) with nitrogen. The back pressure regulator was setfor 500 psig. The contents of the reactor were stirred and heated to93-95° C. for about one hour. At run's end the reactor contents werecooled to room temperature and discharged onto ice. CF₃CH₂F was allowedto evaporate and the lower organic layer separated and analyzed toobtain the following on a CF₃CH₂F-free basis; 19.1% CClF₂CH₂Cl, 38.3%CCl₂FCH₂Cl, 5.8% CCl₃CH₂Cl and 34.3% CHCl═CCl₂. Small amounts (<2.5%) ofother unidentified products were present.

These results show that the hydrogen fluoride which is combined withCF₃CH₂F does indeed react with CHCl═CCl₂ leaving a vapor stream enrichedin CF₃CH₂F.

Example 2 Reaction of Hydrogen Fluoride/1,1,1,2-Tetrafluoroethane withTrichloroethene

The General Experimental Procedure for liquid-phase reactions wasfollowed using TaF₅ (0.5 g, 0.002 mol), CF₃CH₂F (25 mL, 0.30 mol),anhydrous hydrogen fluoride (1.25 mL, 0.063 mol), the HF and CF₃CH₂Famounts were selected so as to simulate an azeotropic composition, andCHCl═CCl₂ (10.0 g, 0.076 mol). The reactor was pressurized to 200 psigwhen cold (−78° C.) with nitrogen. The back pressure regulator was setfor 500 psig. The contents of the reactor were stirred and heated to96-104° C. for about thirty mi nutes. At run's end the reactor contentswere cooled to room temperature and discharged onto ice. Most of theCF₃CH₂F was allowed to evaporate and the lower organic layer separatedand analyzed to obtain the following on a CF₃CH₂F-free basis; 74.0%CClF₂CH₂Cl and 25.9% CHCl═CCl₂. Small amounts (<0.1%) of otherunidentified products were present.

These results show that the hydrogen fluoride which is combined withCF₃CH₂F can react with CHCl═CCl₂ at a reduced catalyst loading andshorter reaction time than in Example 1.

Example 3 Reaction of Hydrogen Fluoride/1,1,1,2-Tetrafluoroethane withTrichloroethene

Example 2 was substantially repeated except that the reactor contentswere heated to 100-105° C. for 15 minutes. Product analysis on aCF₃CH₂F-free basis showed 56.3% CClF₂CH₂Cl and 43.6% CHCl═CCl₂.

Example 4 Reaction of Hydrogen Fluoride/2-Chloro-1,1,2-Tetrafluoroethanewith tetrachloroethene

The General Experimental Procedure for liquid-phase reactions wasfollowed using TaF₅ (see Table 1), CF₃CHClF (18 mL, 0.182 mol),anhydrous hydrogen fluoride (1.25 mL, 0.063 mol), the HF and CF₃CH₂Famounts were selected so as to simulate an azeotropic composition, andCCl₂═CCl₂ (10.0 g, 0.06 mol). The reactor was pressurized to 200 psigwhen cold (−78° C.) with nitrogen. The back pressure regulator was setfor 500 psig. The contents of the reactor were stirred and heated to thetemperatures and for the times shown in Table 1. The reaction productwas worked up as in Examples 1 to 3 and analyzed on a CF₃CHClF-freebasis.

TABLE 1 Reaction Cat. Reaction Products Time Temp. Wt. % CClF₂CHCl₂ %CCl₂FCHCl₂ % CCl₂═CCl₂ 1 h 119-121° C. 0.5 g 1.2 54.3 43.9 1 h 124-127°C. 1.0 g 4.2 57.3 37.3

Example 5

Reaction of Hydrogen Fluoride/Chlorodifluoromethane with Chloroform

The General Experimental Procedure for liquid-phase reactions wasfollowed using TaF₅ (see Table 2), CHClF₂ (20 mL, 0.27 mol), anhydroushydrogen fluoride (0.75 mL, 0.038 mol) and chloroform (10.0 g, 0.084mol). The reactor was pressurized to 200 psig when cold (−78° C.) withnitrogen. The back pressure regulator was set for 500 psig. The contentsof the reactor were stirred and heated to 69-71° C. for two hours. Atrun's end the reactor contents were cooled to room temperature anddischarged onto ice. Most of the CHCLF₂ was allowed to evaporate and thelower organic layer separated and analyzed to obtain the following on aCHClF₂-free basis.

TABLE 2 Cat. Wt. % CHCl₂F % CHCl₃ 0.5 g  9.1 90.9 1.0 g 11.2 88.8

Example 6 Reaction of Hydrogen Fluoride/1,1,1,2-Tetrafluoroethane withTrichloroethene

A ⅝″ I.D. Inconel® reactor was charged with chrome oxide (60 mL, 78 g,12/20 mesh) and heated to 275° C. in a flow of nitrogen (25 cc/min) forabout 20 hours. The temperature was reduced to 175° C. and a 2:1 molarratio of nitrogen and hydrogen fluoride was started through the reactor(total flow 100 ml/min). After one hour under these conditions, themolar ratio of nitrogen to hydrogen fluoride was adjusted to 1:3 and thetemperature increased gradually over a two hour period to 400° C. Thereactor was then brought back to the desired operating temperature, andflow of reactants (Table 3) started.

The product exiting the reactor was analyzed by gas chromatography. Thetable percentages are in mole %.

TABLE 3 Hydrogen Fluoride/ F134a^(a)/ Temp. FC1120^(b) C.T.^(c) F134aF133a^(d) F132b^(e) F1122^(f) FC1120 300° C.  .25/1/0.1* 60 71 23 0 0 0250° C. .25/1/0.1 60 78 22 0 0 0 200° C. .25/1/0.1 60 73 27 0 0 0 160°C. .25/1/0.1 60 70 30 0 0 0 100° C. .25/1/0.1 53 93  1 4 0 2 300° C..25/1/0.4 53 17 80 0 1 0 200° C. .25/1/0.4 53 24 72 0 2 2 150° C..25/1/0.4 53 31 63 0   0.3 5 100° C. .25/1/0.4 53 72 12 1 0 15  ^(a).F134a = CF₃CH₂F ^(b). FC1120 = CHCl═CCl₂ ^(c). C.T. = contact time inseconds ^(d). F133a = CF₃CH₂Cl ^(e). F132b = CClF₂CH₂Cl ^(f). F1122 =CHCl═CF₂ *molar ratio

What is claimed is:
 1. A process wherein a halogenated hydrocarbonstarting material is reacted with HF to produce a fluorination productincluding at least one product compound selected from the groupconsisting of saturated chlorofluorohydrocarbons and fluorohydrocarbonswhich contain from 1 to 6 carbon atoms, characterized by: (1)fluorinating said starting material with HF to provide an initialproduct mixture containing HF and said at least one product compound,the amount of HF for said fluorination being in sufficient excess toazeotropically combine with said at least one product compound; (2)distilling the initial product mixture of (1) to remove HCl and torecover said at least one product compound along with the HF which isazeotropically combined therewith; (3) adding additional halogenatedhydrocarbon material selected from (i) halocarbons of the formulaC_(a)H_(b)Cl_(c)F_(d) where a is 1 to 6, b is 0 to 13, c is 1 to 13, andd is 0 to 13, provided that b+a+d equals 2a+2 when the compound isacyclic and 2a when it is cyclic, and (ii) halo-olefins of the formulaC_(a)H_(b)Cl_(c)F_(d) where a is 2 to 6, b is 0 to 11, c is 1 to 11, andd is 0 to 11, provided b+c+d equals 2a when the compound is acyclic and2a−2 when it is cyclic, to the azeotropic composition recovered in (2)to produce a reactive mixture, the amount of said additional halogenatedhydrocarbon material being a molar amount greater than the HF in saidazeotropic composition and said additional halogenated hydrocarbon beingadditional starting material; and (4) reacting the reactive mixture of(3) in the presence of a fluorination catalyst under fluorinatingconditions to produce a product mixture with reduced HF content, therebyutilizing azeotropically combined HF.
 2. The process of claim 1 whereinat least one product compound is selected from the group consisting ofchlorofluorohydrocarbons.
 3. The process of claim 1 wherein the at leastone product compound is selected from the group consisting offluorohydrocarbons.
 4. The process of claim 1 wherein the at least oneproduct compound has from 1 to 3 carbon atoms.
 5. The process of claim 4wherein the at least one product compound is selected from the groupconsisting of chlorofluorohydrocarbons.
 6. The process of claim 4wherein the at least one product compound is selected from the groupconsisting of fluorohydrocarbons.
 7. The process of claim 1 wherein theat least one product compound has from 1 to 2 carbon atoms.
 8. Theprocess of claim 7 wherein the at least one product compound is selectedfrom the group consisting of chlorofluorohydrocarbons.
 9. The process ofclaim 7 wherein the at least one product compound is selected from thegroup consisting of fluorohydrocarbons.
 10. The process of claim 1wherein the product compound is selected for the group consisting ofCHClF₂, CF₃CHCl₂ and CF₃CHClF.
 11. The process of claim 1 wherein theproduct compound is selected from the group consisting of CHF₂CHF₂ andCF₃CH₂F.
 12. The process of claim 1 wherein: (1) CCl₂═CCl₂ isfluorinated with HF to produce an initial product mixture containing HFand at least one product compound selected from the group consisting ofCF₃CHCl₂ and CF₃CHClF, the amount of HF for said fluorination being insufficient excess to azeotropically combine with said at least oneproduct compound; (2) the initial product mixture of (1) is distilled toremove HCl and to recover said at least one product compound along withthe HF which is azeotropically combined therewith; (3) additionalCCl₂═CCl₂ is added to the azeotropic composition recovered in (2) toproduce a reactive mixture, the amount of said additional CCl₂═CCl₂being a molar amount greater than the HF in said azeotropic composition;and (4) the reactive mixture of (3) is reacted in the presence of afluorination catalyst under fluorinating conditions to produce a productmixture with reduced HF content, thereby utilizing azeotropicallycombined HF.
 13. The process of claim 12 wherein in (1) olefinicimpurities are produced and in (4) olefinic impurities produced in (1)are converted to saturated compounds.
 14. The process of claim 1wherein: (1) CHCl₃ is fluorinated with HF to produce an initial productmixture containing HF and CHClF₂, the amount of HF for said fluorinationbeing in sufficient excess to azeotropically combine with CHClF₂; (2)the initial product mixture of (1) is distilled to remove HCl and torecover said CHClF₂ along with the HF which is azeotropically combinedtherewith; (3) additional CHCl₃ is added to the azeotropic compositionrecovered in (2) to produce a reactive mixture, the amount of saidadditional CHCl₃ being a molar amount greater than the HF in saidazeotropic composition; and (4) the reactive mixture of (3) is reactedin the presence of a fluorination catalyst under fluorinating conditionsto produce a product mixture with reduced HF content, thereby utilizingazeotropically combined HF.
 15. The process of claim 1 wherein: (1)CHCl═CCl₂ is fluorinated with HF to produce an initial product mixturecontaining HF and CF₃CH₂F, the amount of HF for said fluorination beingin sufficient excess to azeotropically combine with said CF₃CH₂F; (2)the initial product mixture of (1) is distilled to remove HCl and torecover said CF₃CH₂F along with the HF which is azeotropically combinedtherewith; (3) additional CHCl═CCl₂ is reacted to the azeotropiccomposition recovered in (2) to produce a reactive mixture, the amountof said additional CHCl═CCl₂ being a molar amount greater than the HF insaid azeotropic composition; and (4) the reactive mixture of (3) isreacted in the presence of a fluorination catalyst under fluorinatingconditions to produce a product mixture with reduced HF content, therebyutilizing azeotropically combined HF.
 16. The process of claim 15wherein in (1) olefinic impurities are produced and wherein in (4)olefinic impurities produced in (1) are converted to saturatedcompounds.
 17. The process of claim 1 wherein in (1) olefinic impuritiesare produced and wherein in (4) olefinic impurities produced in (1) areconverted to saturated compounds.
 18. A method for purifying1,1,1,2-tetrafluoroethane product containing (a) CF₃CH₂F, (b) HF in anamount sufficient to azeotropically combine with said CF₃CH₂F, and (c)easily separated material including HCl, comprising: separating HCl fromsaid product; adding CCl₂═CHCl to provide a reactive mixture containingCF₃CH₂F, HF and CCl₂═CHCl; and bringing the reactive mixture intocontact with a fluorination catalyst in the vapor phase so as todecrease the hydrogen fluoride content.
 19. The method of claim 17wherein the 1,1,1,2-tetrafluoroethane product also contains (d) olefinicimpurities which are converted to saturated compounds during saidcontact with a fluorination catalyst.
 20. The method of claim 11 whereinthe mole ratio of hydrogen fluoride to unsaturated compounds contactedwith the fluorination catalyst is about 2.5:1; and wherein thefluorination catalyst is a fluorinated chrome oxide.